Bacteria, Viruses, and Protists

Historical Interest in Bacteria

What bacterium classification is based on oxygen?

Bacteria can also be divided into four major groups based on their response to oxygen. Aerobic bacteria grow in the presence of oxygen; microaerophilic bacteria grow best at oxygen concentrations lower than those present in air—less than 20 percent oxygen. Anaerobic bacteria grow best in the absence of oxygen; and finally, facultative anaerobes can grow in the presence or absence of oxygen, with more growth when oxygen is present.